Microwave heating apparatus with a vapor generator and regenerating plates

ABSTRACT

A microwave heating apparatus includes a heating chamber  3  for accommodating an item  2  to be heated; a microwave generator  11  for radiating microwaves to the heating chamber  3,  and a vapor generator  12  for supplying vapor to the heating chamber  3 . The heating chamber  3  includes regenerating plates  28   a  and  28   b  for generating and regenerating heat when radiated by the microwaves from the microwave generator  11,  thereby reducing dew condensation caused by the vapor in the heating chamber  3.

TECHNICAL FIELD

The present invention relates to a microwave heating apparatus forquickly heating and cooking food while maintaining the quality of thefood.

BACKGROUND ART

FIG. 22 shows a structure of a conventional microwave heating apparatusincluding a vapor generator.

A main body 1 of the microwave heating apparatus (hereinafter, referredto simply as the “main body 1”) includes a heating chamber 3 foraccommodating an item 2 to be heated (hereinafter, referred to simply asthe “item 2”), a magnetron 4 provided outside the heating chamber 3, anda vapor generator 5 for generating vapor 10 to be supplied to theheating chamber 3. The vapor generator 5 includes a vapor generatingchamber 6 and a water supply tank 7 in communication with the vaporgenerating chamber 6.

The item 2 is heated for cooking by microwaves 8 generated by themagnetron 4 and the vapor 10 supplied to the heating chamber 3 from thevapor generating chamber 6. The vapor generating chamber 6 generatesheat by an electric current induced by an induction heating coil 9 andthus generates the vapor 10.

By heating the item 2 using both the microwaves 8 and the vapor 10, themoisture is maintained in the item 2 more than in the case where onlythe microwaves 8 is used for heating. Moreover, the vapor 10 heats theitem 2 uniformly and thus more satisfactorily.

However, the conventional microwave heating apparatus has the followingproblems.

The microwave heating apparatus requires 2 to 4 minutes to start up,i.e., from the time the induction heating coil 9 is activated until thevapor 10 is generated, as shown in FIG. 23. This prolongs the cookingtime. For 1 to 2 minutes after the induction heating coil 9 isdeactivated, the vapor 10 is still being supplied to the heating chamber3. This can cause some danger when taking the cooked item 2 out from theheating chamber 3.

Furthermore, when the vapor 10 is supplied to the heating chamber 3, thevapor 10 contacts the walls of the heating chamber 3 and thus generatesdew condensation. The microwaves 8 are absorbed by the dew condensation,thereby causing non-uniformity in the electric wave distribution in theheating chamber 3. Thus, uniform heating by the microwaves 8 is notrealized.

The dew condensation also tends to de-sanitize the heating chamber 3.

The present invention has an objective of providing a microwave heatingapparatus for heating and cooking an item by reducing the dewcondensation in a heating chamber.

The present invention has another objective of providing a microwaveheating apparatus for heating and cooking an item, which supplieshigh-speed vapor corresponding to the microwaves so as to realizequicker cooking, more safety in removing the cooked item with no vaporremaining in the heating chamber, and a reduction in dew condensation inthe heating chamber.

DISCLOSURE OF THE INVENTION

According to one aspect of the invention, a microwave heating apparatusincludes a heating chamber for accommodating an item to be heated; amicrowave generator for radiating microwaves to the heating chamber, anda vapor generator for supplying vapor to the heating chamber. Theheating chamber includes a regenerating plate for generating andregenerating heat when radiated by the microwaves from the microwavegenerator, thereby reducing dew condensation caused by the vapor in theheating chamber.

In one embodiment of the invention, the vapor generator includes anexcitation coil provided outside a vapor generating chamber and a metalbody provided inside the vapor generating chamber which is made of oneof foam and fiber. Water from a water supply tank is drip-fed onto a topend of the metal body.

In one embodiment of the invention, the regenerating plate is providedon at least one of top, bottom, left, right and inner rear wallsincluded in the heating chamber.

In one embodiment of the invention, the regenerating plate is on atleast one of an upper position and a lower position with respect to aposition at which the item to be heated is located in the heatingchamber.

In one embodiment of the invention, a microwave heating apparatusfurther includes a control section for pre-heating the regeneratingplate to a prescribed temperature by operating the microwave generatorprior to a supply of the vapor to the heating chamber from the vaporgenerator.

In one embodiment of the invention, a vapor spraying outlet is providedfor releasing the vapor upward from a lower position in the heatingchamber.

In one embodiment of the invention, supporting plate is provided forcovering a side wall of the heating chamber and supporting ends of theregenerating plate, and the regenerating plate has a vapor directionguide formed thereon for releasing the vapor upward to a positioncorresponding to a vapor spraying outlet formed at a lower position ofthe side wall of the heating chamber.

In one embodiment of the invention, a length of the regenerating platein a depth direction is shorter than a length of the heating chamber inthe depth direction, and the heating chamber is structured so that airwarmed by cooling a magnetron of a microwave generator flows in througha gap between at least one of the walls of the heating chamber and theregenerating plate which is set in the heating chamber.

In one embodiment of the invention, a vapor spraying outlet formed atthe lower position on a side wall of the heating chamber is connected toan outlet of a boiler of the vapor generator, and a lower level of thevapor spraying outlet is lower than a lower level of the outlet of theboiler.

In one embodiment of the invention, the regenerating plate includes aplate formed of one of ceramics or porcelain and a glaze layer formed ona surface of the plate, the glaze layer generates heat when radiated bythe microwaves, and the plate regenerates the heat which is generated bythe glaze layer.

In one embodiment of the invention, a microwave heating apparatusfurther includes a control section for pre-heating the heating chamberto a first target temperature by operating the microwave generator priorto the generation of the vapor generator when detecting a pre-heatingstart instruction while being in a wait state, and also for pre-heatingthe heating chamber to a second target temperature which is lower thanthe first target temperature when not detecting any action during aprescribed time period.

In one embodiment of the invention, the vapor generating chamberincludes a diffusive member for diffusing water drip-fed from the watersupply tank.

In one embodiment of the invention, the diffusive member includes an endsurface diffusive member provided at an end surface of the metal bodyand an outer peripheral wall diffusive member provided on an outerperipheral wall of the metal body.

In one embodiment of the invention, the outer peripheral wall diffusivemember is formed of long-fiber assembly having an ability of absorbingliquid and an ability of retaining liquid.

In one embodiment of the invention, the metal body includes a hollowspace. A shaft member is inserted into the hollow space for preventingwater drip-fed from the water supply tank from flowing down from thehollow space without being vaporized.

In one embodiment of the invention, the shaft member is a rolledcylindrical member which has a sufficient spring property to vary anouter diameter thereof.

In one embodiment of the invention, the vapor generator is structured soas to pump the water up into the water supply tank by a pump through awater processing material cartridge attached to the water supply tank.

In one embodiment of the invention, a microwave heating apparatusfurther includes a control section for determining time to exchange thewater processing material cartridge based on the operation time of thevapor generator or the operation time of the pump for pumping up thewater from the water supply tank, or the result of accumulation ofamount of supplied water, and for notifying the time to exchange.

In one embodiment of the invention, a microwave heating apparatusfurther includes a control section for stopping the operation of thepump by detecting that the time to exchange the water processingmaterial cartridge is approaching and for allowing the operation of thepump only during a prescribed time period by detecting an inputoperation for instructing a re-start while the operation of the pump isstopped.

In one embodiment of the invention, a microwave heating apparatusfurther includes an input device for inputting a set value for the timeto exchange the water processing material cartridge.

In one embodiment of the invention, a microwave heating apparatusfurther includes a control section for notifying water supply when awater level detector detects that a water level in the water supply tankhas reached a detection level and for still continuing the operation ofthe vapor generator for a prescribed time period.

In one embodiment of the invention, the water level detector includes afloat having a buried magnet mounted in the water supply tank and a leadswitch provided at a position separated from the water supply tank.

In one embodiment of the invention, the detection level is above aninlet of the water processing material cartridge attached to the watersupply tank.

In one embodiment of the invention, a waste water tank is provided at alower position of a main body of the microwave heating apparatus forreceiving water from the dew condensation in the heating chamber and thewater discharged from the boiler of the vapor generator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external view of a microwave heating apparatus in anexample according to the present invention.

FIG. 2 is a left side view of the microwave heating apparatus shown inFIG. 1.

FIG. 3 is a cross-sectional view of the microwave heating apparatusshown in FIG. 1 seen from the front side thereof.

FIG. 4 is an isometric view of a heating chamber of the microwaveheating apparatus shown in FIG. 1 in the state where components areremoved.

FIG. 5 is an exploded isometric view of the components of the heatingchamber.

FIG. 6 is an isometric view of the heating chamber in the state wherethe components are assembled.

FIG. 7 is a cross-sectional view of a regenerating plate.

FIG. 8 is a view illustrating the structure of a vapor generator.

FIG. 9 is a view illustrating the structure of a boiler of the vaporgenerator.

FIG. 10 shows a configuration of an electric circuit mounted in a mainbody of the microwave heating apparatus.

FIG. 11 is a timing diagram of a pre-heating and stand-by routine.

FIG. 12 shows an operational timing of a cooking processing routine.

FIG. 13 shows another operational timing of a cooking processingroutine.

FIG. 14 shows still another operational timing of a cooking processingroutine.

FIG. 15 shows yet another operational timing of a cooking processingroutine.

FIG. 16 is a flowchart of a cartridge exchange time notificationroutine.

FIG. 17 is a flowchart of a safety routine.

FIG. 18 is a view illustrating the state where a water processingmaterial cartridge is not mounted.

FIG. 19 is a flowchart of another cartridge exchange time notificationroutine.

FIG. 20 a flowchart of still another cartridge exchange timenotification routine.

FIG. 21 is a flowchart of a water supply time notification routine.

FIG. 22 is a view illustrating a structure of a conventional microwaveheating apparatus.

FIG. 23 is a timing diagram of cooking processing of the conventionalmicrowave heating apparatus.

BEST MODE FOR CARRYING THE INVENTION

Hereinafter, the present invention will be described by way ofillustrative examples with reference to the accompanying drawings.

As shown in FIGS. 1, 2 and 3, a main body 1 of a microwave heatingapparatus 100 (hereinafter, referred to simply as the “main body 1”)includes a heating chamber 3 for accommodating an item 2 to be cooked(hereinafter, referred to simply as the “item 2”), a microwave generator11 for radiating microwaves toward the heating chamber 3, and a vaporgenerator 12 for generating vapor to be supplied to the heating chamber3.

A first door 13 is attached to the main body 1 to be allowed to beopened and closed. The first door 13 is opened and closed so as to putin and take out the item 2 from the heating chamber 3. A second door 14is attached to the main body 1 to be allowed to be opened and closed.The second door 14 is opened and closed around a shaft 16 so as toattach and detach a water supply tank 15 to and from the vapor generator12. The second door 14 has a window 17 to allow the user to visuallycheck the water level in the water supply tank 15.

The microwave generator 11 includes a magnetron 4 provided outside theheating chamber 3, an antenna 18 provided on the ceiling of the heatingchamber 3, and a waveguide 19 for supplying the microwaves generated bythe magnetron 4 to the antenna 18. The magnetron 4 is forcibly cooled bya fan 20.

FIG. 4 shows an inner structure of the heating chamber 3. As shown inFIG. 4, the heating chamber 3 has top and bottom walls, two side walls,and an inner rear wall. The inner rear wall has holes 22 in an upperpart thereof. The two side walls each have a hole 23 in an upper partthereof. These walls in the heating chamber 3 are made of stainlesssteel and shaped like a box.

FIG. 5 shows components of the heating chamber 3. The components areassembled in the following order.

First, in the state where the first door 13 is opened, a top plate 21 isset at a prescribed position in the heating chamber 3. The top plate 21is set so as not to expose the antenna 18 (FIG. 4). The top plate 21 hasprojections 21 a and elastic parts 21 b. The projections 21 a areprovided on a rear side thereof, and the elastic parts 21 b areintegrally formed at both two sides of the front of the top plate 21.The elastic parts 21 b each have a projection 21 a. The top plate 21 isset at the prescribed position in the heating chamber 3 by inserting theprojections 21 a into the holes 22 (FIG. 4) in the inner rear wall ofthe heating chamber 3 and inserting the projections 21 a into the holes23 (FIG. 4) formed on the side walls of the heating chamber 3.

Next, supporting plates 24 a and 24 b are set at prescribed positionsalong the side walls in the heating chamber 3. The top ends of thesupporting plates 24 a and 24 b engage the elastic parts 21 b of the topplate 21 (FIG. 6). The supporting plates 24 a and 24 b have supportingrails 25 integrally formed thereon.

The supporting plates 24 a and 24 b are identical in shape forconvenience in use.

A plate 27 has a plurality of holes 26. The plate 27 is inserted intothe heating chamber 3 along the supporting rails 25 of the supportingplates 24 a and 24 b. The item 2 (FIG. 3) is to be placed on the plate27.

A regenerating plate 28 a is set at a prescribed position in the heatingchamber 3 above the plate 27 (FIG. 6). A regenerating plate 28 b is setat a prescribed position in the heating chamber 3 below the plate 27(FIG. 6).

FIG. 7 shows a structure of the regenerating plates 28 a and 28 b. Theregenerating plates 28 a and 28 b are each formed by baking a ceramic(or porcelain) plate 29 having glaze 30 applied thereon. The ceramic (orporcelain) plate 29 can be, for example, mullite quartz ceramic. Theregenerating plates 28 a and 28 b each includes the ceramic (orporcelain) plate 29 and the layer of glaze 30 formed on a surface of theceramic (or porcelain) plate 29. When the microwaves are radiated to theregenerating plates 28 a and 28 b, the layer of the glaze 30 generatesheat. Such heat is regenerated by the ceramic or porcelain plate 29.

FIG. 8 shows a structure of a vapor generator 12. The vapor generator 12includes a vapor generating chamber (boiler) 31 attached to the mainbody 1, a magnetic excitation coil 32 wound around the boiler 31, a foamor fiber metal body 33 provided inside the boiler 31, and the watersupply tank 15 detachable with respect to the main body 1.

The water supply tank 15 is attached to the main body 1 in the followingmanner.

The second door 14 (FIG. 1) is opened, and the water supply tank 15 isinserted while being put on a bottom plate 34. Thus, a nozzle 36 of thewater supply tank 15 is inserted into a connection opening 35 providedon the main body 1. A hook 37 attached to the main body 1 engages thewater supply tank 15, thereby restricting the movement of the watersupply tank 15. In this manner, the water supply tank 15 is attached tothe main body 1.

The connection opening 35 is connected to an inlet of a pump 39 througha tube 38 a. An outlet of the pump 39 is connected to a top end of theboiler 31 through a tube 38 b. Due to such a system, water from thewater supply tank 15 is drip-fed onto the metal body 33.

A water processing material cartridge (ion exchange resin cartridge) 40is attached to the water supply tank 15. When the pump 39 is operated,the water in the water supply tank 15 is pumped up through the waterprocessing material cartridge 40. Thus, water is supplied to the boiler31 excluding any scale component (contained in tap water).

FIG. 9 shows a structure of a heating generation section of the boiler31. The metal body 33 is cylindrical. The metal body 33 has adisc-shaped unglazed chip 41 at a top end thereof. A ceramic paper sheet42 is provided on the unglazed chip 41. The ceramic paper sheet 42 isheat-resistant and acts as an end surface diffusive member for diffusingthe water in a horizontal direction. The unglazed chip 41 retainsmoisture satisfactorily but does not absorb water sufficiently quickly,whereas the ceramic paper sheet 42 does retain moisture satisfactorilyand also absorbs water sufficiently quickly. The unglazed chip 41 has aliquid introduction groove 43 for efficiently introducing water whichhas been drip-fed and diffused into an outer peripheral surface of themetal body 33.

The metal body 33 is wrapped around by a ceramic cloth 44, which acts asan outer peripheral wall diffusive member for diffusing drip-fed waterto the outer peripheral wall of the metal body 33. The ceramic cloth 44is formed by processing ceramic long-fiber assembly into cloth. The useof the ceramic cloth 44 provides the advantages of improving the abilityof retaining moisture and also raising the water absorption speed.

The water drip-fed from the top end of the boiler 31 is quickly absorbedinto the ceramic paper sheet 42 and diffused into the entirety thereof,and then uniformly absorbed into the unglazed chip 41. Then, a part ofthe water flows down along the metal body 33 from the unglazed chip 41,whereas most of the water flows down along the ceramic cloth 44 providedaround the metal body 33.

A shaft member 45 is inserted into the hollow space in the cylindricalmetal body 33. The shaft member 45 prevents water drip-fed from the topend of the boiler 31 from flowing down the hollow space without beingvaporized. The outer diameter d1 of the shaft member 45 is larger thanthe diameter d2 of the hollow space of the metal body 33 acting as aheat generator. The shaft member 45 is a rolled cylindrical member andhas a sufficient spring expansion property to vary the outer diameterthereof. The shaft member 45 is kept in the hollow space in the metalbody 33 by the extending force of the spring.

When the magnetic excitation coil 32 (FIG. 8) is excited, the metal body33 is induced and thus quickly heated into a high temperature. As aresult, the water drip-fed down the metal body 33 is heated whilepassing through the foam of the metal body 33 between the ceramic cloth44 and the shaft member 45. The heated water is further heated whileflowing downward and splashed from the downstream end of the metal body33 or of a shaft member 45. After that, the water is sprayed as thevapor 10 from a vapor outlet 46 (FIG. 8) while in the state of beingexcessively heated.

Referring again to FIG. 8, the vapor 10 sprayed from the vapor outlet 46is released into the heating chamber 3 upward from this lower positionthrough a spraying outlet 47.

The vapor outlet 46 is attached so as to be opposed to the vaporspraying outlet 47 provided in a lower part of the left side wall of theheating chamber 3. The supporting plates 24 a have a vapor directionguide 48 (also shown in FIG. 3) integrally formed in correspondence withthe vapor spraying outlet 47. The vapor direction guide 48 has an upwardoutlet. Accordingly, the vapor 10 sprayed from the vapor outlet 46 isreleased upward to an upper part of the heating chamber 3 through thevapor direction guide 48.

FIG. 10 shows a configuration of an electric circuit mounted in the mainbody 1.

A control section 49 controls the execution of various routines such asa cooking processing routine 50, a pre-heating and stand-by routine 51,a cartridge exchange time notification routine 52, and a water supplytime notification routine 53. The control section 49 can also include amicrocomputer.

After the item 2 is placed on the plate 27 (FIG. 3), the control section49 can execute the cooking processing routine 50. Before the cookingprocessing routine 50 is executed, the control section 49 executes thepre-heating and stand-by routine 51. Thus, the heating chamber 3 ispre-heated.

Pre-heating and Stand-by Routine

FIG. 11 shows the operation of the pre-heating and stand-by routine 51.The pre-heating and stand-by routine 51 is executed in a wait state.

When the control section 49 determines that the microwave heatingapparatus is put into the wait state, the control section 49 detectswhen any key of an input key group 54 is operated, or automaticallyswitches the mode of the pre-heating and stand-by routine 51 from mode Ato mode B, and from mode B to mode C over time until it is detected by asignal from the door switch 55 that the first door 13 has been opened.

In an upper part of the heating chamber 3, a temperature sensor 56 isprovided as shown in FIGS. 3 and 4. In mode A, the temperature in theheating chamber 3 is controlled so as to be 70±10° C. As shown in (b)and (d) in FIG. 11, the operation of the magnetron 4 and the fan 20commences from the start P of pre-heating.

When the microwaves are radiated in the heating chamber 3, the entiretyof each of the regenerating plates 28 a and 28 b generates heat. Thesupporting plates 24 a and 24 b formed of PPS (polyphenylene sulfide)also generate heat when irradiated by the microwaves although thetemperature of the heat is lower than the heat generated by theregenerating plates 28 a and 28 b.

By operating the fan 20, a part of the warm air W (FIG. 3) which hasbecome warm by cooling the magnetron 4 is released into the heatingchamber 3 through the hole 57 (FIGS. 4 and 6) formed in the inner rearwall of the heating chamber 3. The released warm air Wa is sent to afront part of the heating chamber 3 while being guided, by a partition21 d provided on the top plate 21, between a top wall 3 b and the topplate 21. From the front end of the top plate 21, the warm air Wa flowsinto a space where the plate 27 is set from the right through a gap Sbetween a front end of the regenerating plate 28 a and the first door13.

The air in the space where the plate 27 is set is discharged outsidethrough an outlet 58 (FIG. 4) formed in a left part of the top wall 3 bof the heating chamber 3 as described below.

The outlet 58 is in communication with the regenerating plate 28 a andthe top plate 21 through a duct 21 e (FIG. 5) formed on the top plate21. Air Wb in the space where the plate 27 is set flows from the leftside to between the regenerating plate 28 a and the top plate 21 and isdischarged outside through an outlet 58.

In this manner, the air in the heating chamber 3 is circulated byoperating the fan 20. The operation of the magnetron 4 continues untilthe temperature detected by the temperature sensor 56 becomes 80° C.Portion (a) of FIG. 11 shows the temperature in the heating chamber 3.The operation of the fan 20 continues for a while even after theoperation of the magnetron 4 is stopped in order to cool the components.Even while the magnetron 4 is in a pause, the fan 20 is operatedregularly. Thus, the air in the heating chamber 3 is circulated. Whenthe temperature detected by the temperature sensor 56 is reduced to 60°C., the control section 49 starts operating the magnetron 4. In thismanner, the temperature in the heating chamber 3 is controlled to be70±10° C.

Portion (c) of FIG. 11 shows the period in which the excitation coil 32is driven. The excitation coil 32 is driven by an excitation coil driver59 (FIG. 10) from when the temperature detected by the temperaturesensor 56 becomes close to 80° C. (80° C.−Δ) until such a temperaturebecomes 80° C. Thus, the boiler 31 in the vapor generator 12 ispre-heated.

In the case where the microwave heating apparatus is still in the waitstate even after the operation time period of mode A reaches aprescribed time period, the control section 49 executes the pre-heatingand stand-by routine 51 in mode B for the purpose of saving energy. Inmode B, the target temperature is set to be 60±10° C., which is lowerthan 70±10° C. A similar temperature control to the operation in mode Ais executed.

In the case where the microwave heating apparatus is still in the waitstate even after the operation time period of mode B reaches aprescribed time period, the control section 49 executes the pre-heatingand stand-by routine 51 in mode C for the purpose of saving energy, andterminates the temperature control.

In either mode B or mode C, when the control section 49 detects that anykey of the input key group 54 is operated, the pre-heating and stand-byroutine 51 is immediately returned to mode A and performs pre-heating.

Cooking Processing Routine

In the cooking processing routine 50, based on the data input by theinput key group 54, the operation pattern of the magnetron 4 and theoperation pattern of the excitation coil driver 59 are selected. Inaccordance with the selected operation patterns, the microwaves 8 andthe vapor 10 are generated. By use of the microwaves 8 and the vapor 10,the item 2 is properly cooked.

More specifically, for the cooking processing routine 50, one of theoperation patterns shown in FIGS. 12 through 15 is selected.

In the operation pattern shown in FIG. 12, the rise of the vaporgeneration by the vapor generator 12 takes as short a time period asabout 10 seconds. Accordingly, the vapor from the vapor generator 12 issupplied to the heating chamber 3 substantially simultaneously with thestart of the operation of the microwaves. As a result, both of themicrowaves 8 and the vapor 10 are substantially used during the entiretime for heating for cooking. This restricts vaporization of themoisture in the food as the item 2 and realizes a more tender finish.

Before the cooking processing routine 50 is executed, the pre-heatingand stand-by routine 51 is executed and thus the heating chamber 3 iswarmed up inside. Accordingly, even if the vapor 10 supplied to theheating chamber 3 immediately after the execution of the cookingprocessing routine 50 is started, dew condensation does not form on thewall of the heating chamber 3.

Since there is no dew condensation, unnecessary electric wave absorptionis not caused and also non-uniformity in the microwave distribution inthe heating chamber 3 due to this dew condensation is avoided. As aresult, a satisfactory heating state is obtained.

Moreover, the vapor 10 supplied to the heating chamber 3 is releasedinto an upper part of the heating chamber 3 through the vapor directionguide 48 which is integrally formed on the supporting plate 24 a. Thus,the vapor 10 is not in direct contact with the food. Accordingly, thetemperature distribution in the heating chamber 3 is uniform, andheating is performed uniformly over the food.

Also in the other operation patterns shown in FIGS. 13 through 15,execution of the pre-heating and stand-by routine 51 before the cookingprocessing routine 50 avoids creation of dew condensation when the vapor10 is supplied to the heating chamber 3.

The operation pattern shown in FIG. 13 is selected for heating andcooking frozen food. While the food is frozen, i.e., the temperature ofthe food is below 0° C., the food is heated only by the microwaves 8.Then, when the food is thawed and the temperature of the food risesabove 0° C., the operation of the vapor generator 12 is started so as toperform heating for cooking by use of both the microwaves 8 and thevapor 10. The vaporization of the moisture from the food starts when thetemperature of the food becomes above 0° C. However, such vaporizationis restricted by cooking while wrapping the food with vapor, therebyrealizing a more tender finish.

In the operation pattern shown in FIG. 14, the vapor 10 from the vaporgenerator 12 is supplied to the heating chamber 3 substantiallysimultaneously with the start of the operation of the microwaves, andthe operation of the vapor generation is finished before the operationof the microwaves finishes. In such a case, the amount of vapor 10 inthe heating chamber 3 is reduced at the end of cooking. Thus, the foodis easily taken out without the user coming into contact with thehigh-temperature vapor.

The operation pattern shown in FIG. 15 is another pattern which isselected for heating frozen food for cooking. While the food is frozen,the food is heated for cooking by use of high-output microwaves 8 andlow-output vapor 10 from the vapor generator 12. Then, when the food isthawed and the temperature of the food becomes above 0° C., the outputof the microwaves 8 is decreased to a middle level and the output of thevapor 10 is increased to a middle level. When the temperature of thefood is raised to a middle level, the output of the microwaves 8 isdecreased to a low level and the output of the vapor 10 is increased toa high level.

In such a case, the food can be heated uniformly while vaporization ofthe moisture is restricted. Thus, a more tender finish is realized.

Cartridge Exchange Time Notification Routine

FIG. 16 shows the steps of the cartridge exchange time notificationroutine 52. The control section 49 is structured to control theoperation time of the pump 39 in accordance with the cartridge exchangetime notification routine 52 and to notify the exchange time of thewater processing material. To use the cartridge exchange timenotification routine 52, set time A for exchange notification and settime B for prohibiting the operation (B≧A) are set in advance.

In #1, it is checked whether the set time A and B are to be initiallyset or not. If no initial setting is to be performed, #2 is executed. Ifinitial setting is performed in #1, #2 is executed after the content (T)in the register is reset.

In #2, it is checked whether the pump 39 is operating or not. If it isdetermined that the pump 39 is operating in #2, the operation time ofthe pump 39 is counted in #4 by the register which was reset in #3.Then, #5 is executed. If it is determined that the pump 39 is notoperating in #2, #5 is executed without executing #4.

In #5, the content (T) in the register which counted the operation timeof the pump 39 in #4 and the set time A for exchange notification arecompared. If it is determined that T≧A in #5, an instruction for waterprocessing material exchange is displayed on a display 60 (FIG. 1) of anoperation panel in #6. If it is determined that T<A in #5, #7 isexecuted.

In #7, it is checked whether a flag for instructing the operation of thevapor generator 12 is set or not. If it is determined that the flag forinstructing the operation of the vapor generator 12 is not set in #7,the operation of the pump 39 and the vapor generator 12 is stopped in#8. If it is determined that the flag for instructing the operation ofthe vapor generator 12 is set in #7, the content (T) of the registerwhich counted the operation time of the pump 39 in #4 and the set time Bare compared in #9. If it is determined that T≧B in #9, an instructionfor prohibiting the operation of the vapor generator 12 is displayed onthe display 60 of the operation panel in #10. Then, #8 is executed. Ifit is determined that T<B in #9, #11 is executed. In #11, the operationof the pump 39 and the vapor generator 12 is performed.

The set time A is keyed in by the input key group 54 in accordance withthe water quality at the site of installment when the microwave heatingapparatus is installed. Specifically, the water quality of the site inuse is measured by a water hardness reagent and the water hardnessmeasurement is keyed-in by the input key groups 54. More specifically,when the water hardness obtained by the measurement using the waterhardness reagent is one of 50, 100 or 200, switching into the operationinformation key-in mode is performed and then the water hardnessobtained by the measurement is keyed-in. In this example, while thefirst door 13 is opened, a specific key (for example, a cooking startswitch) of the input key group 54 is kept pressed. In this state, aspecific code is keyed-in, thereby switching the control section 49 intothe operation information key-in mode. In the case where the waterhardness obtained by the measurement is 50, “5” and “0” are keyed-in. Inthis case, the control section 49 sets the count value corresponding tothe operation time of the pump 39 which is required to supply 600 litersof water as the set time A, and executes the cartridge exchange timenotification routine 52.

In the case where the water hardness obtained by the measurement is 100,the control section 49 sets the count value corresponding to theoperation time of the pump 39 which is required to supply 300 liters ofwater as the set time A, and executes the cartridge exchange timenotification routine 52.

In the case where the water hardness obtained by the measurement is 200,the control section 49 sets the count value corresponding to theoperation time of the pump 39 which is required to supply 150 liters ofwater as the set time A, and executes the cartridge exchange timenotification routine 52.

Safety Routine

As shown in FIG. 8, the main body 1 includes a detachable sensor 61 fordetecting that the water supply tank 15 is properly set, and a waterlevel detector 62 for detecting the water level in the water supply tank15. The water level detector 62 includes a magnetic float 63incorporated into the water supply tank 15 and a float sensor 64incorporated into the bottom plate 34 for detecting the position of themagnet float 63.

As shown in FIG. 17, when the control section 49 detects the power hasbeen turned on in #12, the control section 49 checks the detachablesensor 61 in #13 and checks the float sensor 64 in #14. Then, thecontrol sensor 49 checks whether the start key in the input key group 54has been operated or not in #15.

Accordingly, only when the water supply tank 15 is properly set in themain body land water in at least a minimum possible amount remains, theoperation of the vapor generator 12 starts in response to the input bythe start key (#15, #16). If the water supply tank 15 is not properlyset in the main body 1 or the water level is not sufficiently high, theoperation of the vapor generator 12 is stopped in #17. Thus, safeoperation of the vapor generator 12 is guaranteed.

The water processing material cartridge 40 is inserted from below into acorresponding part of a lid 15 a of the water supply tank 15 and pivotedby a prescribed angle for locking, thereby being attached to the watersupply tank 15. Such an attachment makes it easier to exchange the waterprocessing material cartridge 40. The water supply tank 15 is structuredso that a connection position J (FIG. 8) between the lid 15 a and thewater processing material cartridge 40 is above the highest water levelof the water supply tank 15. Accordingly, when the water supply tank 15is operated without mounting the water processing material cartridge 40,water is not supplied to the vapor genera 12 even if the pump 39 isoperated. Thus, the water containing a scale component is avoided frombeing erroneously supplied to the metal body 33, and thus from cloggingthe metal body 33.

In the state where the water processing material cartridge 40 is notmounted, water is not supplied to the metal body 33 even if the pump 39is operated. This raises the temperature of the metal body 33abnormally. In this example, the control section 49 monitors thetemperature of the metal body 33 using a thermal switch 65 so that theoperation of the excitation coil driver 59 is stopped when such anabnormal temperature rise is detected.

When the water drip-fed on the metal body 33 is not completelyvaporized, a water puddle is generated in the vicinity of the vaporoutlet 46 of the vapor generator 12. In this example, as shown in FIG.8, the lower level of the vapor outlet 46 is set to be lower than thelevel K (FIG. 8) of the vapor spraying outlet 47 in the heating chamber3. Accordingly, even if a water puddle is generated in the vicinity ofthe vapor outlet 46, such water does not flow into the heating chamber 3through the water spraying outlet 47.

The water puddle generated in the vicinity of the water outlet 46 flowsdown to a waste water tank 67 from a discharge outlet 46 a through atrap 66. The waste water generated in the heating chamber 3 is receivedby a conduit 68 and flows into the waste water tank 67.

In this example, the time for exchanging the water processing materialcartridge 40 to be notified is determined based on the operation time ofthe pump 39. Alternatively, such time can be determined based on theoperation time of the vapor generator 12 as shown in FIG. 19 or based onthe water amount supplied by the pump 39 as shown in FIG. 20. In FIG.20, letter V represents the result of accumulation of the water amountsupplied by the pump, letter Q represents the flow rate of the pumpwhich is set per unit time, and letter T represents the sampling timeinterval.

In the above examples, upon the detection that the water processingmaterial cartridge 40 has reached the exchange time, the boiler 31 andthe pump 39 are stopped. In the example shown in FIG. 16, a waterprocessing material cartridge 40 is exchanged with a new one, and thesame register content which was reset in #3 is reset and the routinereturns to #1. At this point, the operation resumes for the first timeafter the exchange. Alternatively, the control section 49 can bestructured to stop the operation upon the detection that the waterprocessing material cartridge 40 has reached the exchange time and todetect the input operation for re-start and allow the operation only fora prescribed time period. By such a system, the user can use themicrowave heating apparatus even while a new water processing materialcartridge 40 is being prepared. It is expected that the work efficiencyis improved by such a system. This can also be applied to the case wherethe time for exchanging the water processing material cartridge 40 isdetermined based on the operation of the boiler 31 or the water amountsupplied by the pump.

In the above-described example, two regenerating plates 28 a and 28 bare used. A regenerating plate can be provided on at least one surfaceof the top, bottom, left, right and inner rear walls of the heatingchamber 3. Such an arrangement of the regenerating plate is effectivefor restricting the creation of dew condensation when the vapor 10 issupplied into the heating chamber 3.

Water Supply Notification Routine

As shown in FIG. 21, the water supply notification is controlled basedon the exchange notification based on a detection signal from the floatsensor 64 and also on set time C for prohibiting the operation of thevapor generator 12. The water level detected by the float sensor 64 isabove the inlet of the water processing material cartridge 40, and thuswater supply to the vapor generator 12 is possible even after the floatsensor 64 operates. The float sensor 64 includes a float having a buriedmagnet mounted in the water supply tank 15 and a lead switch provided ata position separated from the water supply tank 15.

When the water supply tank 15 is properly mounted, the vapor generator12 is properly operated in #18. The control section 49 checks the floatsensor 64 in #19. If a water level is not detected in #19, the operationof the vapor generator 12 in #18 is continued. If a water level isdetected in #19, the water supply notification is displayed on thedisplay 60 of the operation panel #20 and also supplementary operationis performed in #21. In #22, the operation time is counted. In #23, thecontent (K) in the counting register and the supplementary operationtime C are compared. If it is determined that K≧C in #23, instructionsfor supplying water to the water supply tank 15 and for prohibiting theoperation of the vapor generator 12 are displayed on the display 60 ofthe operation panel in #24. Then, the operation of the vapor generator12 is stopped in #25. If it is determined that K<C in #23, thesupplementary operation is allowed in #21, and the operation time isaccumulated in #22.

As described above, by providing supplementary operation time andallowing the vapor generation to continue even after the water supplynotification, the vapor generator is prevented from stopping when thevapor is used for cooking. Thus, cooking can be continued even duringwater supply.

The same effects can be obtained by setting the supplementary operationtime by comparing the signal from the water level detector to thenotified water level and the water level at which the operation isprohibited.

INDUSTRIAL APPLICABILITY

In a microwave heating apparatus according to claim 1, the heatingchamber includes a regenerating plate for generating and regeneratingheat when radiated by the microwaves from the microwave generator. Bysupplying the vapor to the heating chamber in the state where theregenerating plate is heated, dew condensation can be reduced.

In a microwave heating apparatus according to claim 2, the vaporgenerator includes an excitation coil provided outside a vaporgenerating chamber and a metal body provided inside the vapor generatingchamber which is formed of one of foam and fiber, and water from a watersupply tank is drip-fed on a top end of the metal body. Thus, dewcondensation can be reduced, and the vapor can be supplied to the heatchamber. Thus, the time required for cooking can be shortened.

In a microwave heating apparatus according to claim 3 or 4, theregenerating plate is provided at a specified position. Such anarrangement of the regenerating plate enables efficient heating of theregenerating plate by microwaves radiated to the heating chamber. Thisis effective in preventing dew condensation when the vapor is suppliedinto the heating chamber.

In a microwave heating apparatus according to claim 5, a control sectionis provided for pre-heating the regenerating plate to a prescribedtemperature by operat the microwave generator prior to the supply of thevapor to the heating chamber from the vapor generator. By suchpre-heating, the regenerating plate is heated to a prescribedtemperature at the time when the vapor is supplied to the heatingchamber. As a result, generation of dew condensation when the vapor issupplied to the heating chamber is prevented certainly.

In a microwave heating apparatus according to claim 6, a vapor sprayingoutlet is provided for releasing the vapor upward from a lower positionin the heating chamber. The vapor supplied to the heating chamber isblown into an upper position of the heating chamber and then moves intoa lower position of the heating chamber at which the item to be heatedis set. Since the vapor does not get into direct contact with the itemto be heated, the item can be heated uniformly for cooking.

In a microwave heating apparatus according to claim 7, a supportingplate is provided for covering a side wall of the heating chamber andsupporting ends of the regenerating plate, and the regenerating platehas a vapor direction guide formed thereon for releasing the vaporupward to a position corresponding to a vapor spraying outlet formed ata lower position of the side wall of the heating chamber. The vaporsupplied to the heating chamber is blown into an upper position of theheating chamber and then moves into a lower position of the heatingchamber where the item to be heated is set. Since the vapor does not getinto direct contact with the item to be heated, the item can be heateduniformly for cooking.

In a microwave heating apparatus according to claim 8, a length of theregenerating plate in a depth direction is shorter than a length of theheating chamber in the depth direction, and the heating chamber isstructured so that air warmed by cooling a magnetron (oscillation tube)of a microwave generator flows in through a gap between at least one ofthe walls of the heating chamber and the regenerating plate which is setin the heating chamber. By such a structure, warm air is supplied intothe heating chamber so that the air in the heating chamber supplied withthe vapor is circulated, without providing a special heating apparatusfor heating air. This is effective in restricting the generation of dewcondensation and making the temperature in the heating chamber uniform.

In a microwave heating apparatus according to claim 9, a vapor sprayingoutlet formed at the lower position on a side wall of the heatingchamber is connected to an outlet of a boiler of the vapor generator,and a lower level of the vapor spraying outlet is lower than a lowerlevel of the outlet of the boiler. Thus, water flowing down withoutbecoming vapor is prevented from being flowing into the heating chamber.

In a microwave heating apparatus according to claim 10, the regeneratingplate efficiently regenerates the heat generated by radiation of themicrowaves. Thus, the surface of the regenerating plate can bepre-heated to a uniform temperature. This is effective in restrictingthe generation of dew condensation when the vapor is supplied to theheating chamber.

In a microwave heating apparatus according to claim 11, the controlsection pre-heats the heating chamber to a first target temperatureunder a certain condition and pre-heats the heating chamber to a secondtarget temperature under another condition. By switching the targettemperature, energy-saving operation can be realized without spoilingthe functions of the microwave heating apparatus.

In a microwave heating apparatus according to claim 12, the waterdrip-fed from the water supply tank reaches the metal body while beinguniformly diffused by a diffusive member. By this, the heatingefficiency of the metal body is improved and liquid is prevented fromflowing down without being vaporized. Since the temperature of the heatgenerating body is reduced, the deterioration of the heat generatingbody by the heat is restricted, thus improving the durability thereof.

In a microwave heating apparatus according to claim 13, the waterdrip-fed from the water supply tank reaches the metal body while beinguniformly diffused by an outer peripheral wall diffusive member.Diffused water is heated on the outer peripheral wall where the heatingtemperature is the highest. As a result, the heating efficiency israised and heating speed is increased.

In a microwave heating apparatus according to claim 14, the outerperipheral wall diffusive member is formed of long-fiber assembly. Thewater which has reached the top end of the outer peripheral walldiffusive member flows down uniformly. Moreover, since the long-fiberassembly retains the liquid in the gap among the fibers, the liquidsupplied to the heat generating body is prevented from flowing downwithout being vaporized. By processing the long-fiber assembly into acloth, the capillary function and the ability of retaining the moistureare improved, and fiber disturbance is reduced. Thus, the attachment ofthe outer peripheral wall diffusive material to the heat generating bodybecomes easy.

In a microwave heating apparatus according to claim 15, water passesthrough the cylinder passage defined by the inner wall of the metal bodyand the shaft member. Accordingly, the heating efficiency can beimproved. Since the heated vapor is diffused at a high speed in the heatgenerating body so as to heat the liquid which has not been vaporized,the heating temperature distribution of the metal body is made uniform,thereby improving the durability.

In a microwave heating apparatus according to claim 16, the shaft membercan be inserted into the hollow space in the metal body while the outerdiameter of the shaft member is reduced. Thus, the attachment of theshaft member to the metal body becomes easy. After the shaft member isinserted into the hollow space in the metal body, the shaft member ispushed onto the inner wall of the metal body by the extending force ofthe spring. Thus, the shaft member is certainly secured. Since theadherence between the shaft member and the metal body is improved, theheated liquid is prevented from flowing out of the passage of the heatgenerating body. As a result, the efficiency of vaporization of theliquid by heating is improved.

In a microwave heating apparatus according to claim 17, the vaporgenerator is structured so as to pump the water up into the water supplytank by a pump through a water processing material cartridge attached tothe water supply tank. Even if the microwave heating apparatus isoperated without mounting the water processing material cartridge, watercontaining any scale component is not provided to the metal body. Thus,clogging of the metal body by malfunction can be prevented.

In a microwave heating apparatus according to claim 18, the controlsection notifies the time to exchange the water processing materialcartridge. Thus, the microwave heating apparatus is prevented fromoperating beyond the time to exchange the water processing materialcartridge. Moreover, it is possible to urge the user to exchange thewater processing material cartridge before the function of the cartridgeis deteriorated. This guarantees the long-time safe operation of themicrowave heating apparatus.

In a microwave heating apparatus according to claim 19, the controlsection allows the operation of the pump under a specific conditionafter stopping the operation of the pump by detecting that the time toexchange the water processing material cartridge is approaching. Thus,the user can use the microwave heating apparatus even while preparingfor a new water processing material cartridge. As a result, the workefficiency of the microwave heating apparatus is increased.

In a microwave heating apparatus according to claim 21, the controlsection notifies the water supply when a water level detector detectsthat the water level in the water supply tank has reached a detectionlevel and still continues the operation of the vapor generator for aprescribed time period. Since the generation of the vapor is continuedeven after the water supply notification, interruption of avapor-utilizing function can be avoided.

In a microwave heating apparatus according to claim 22, the water leveldetector can separate the liquid container from the vapor generator.Accordingly, supply of water to the liquid container and the washing ofthe liquid container can be conducted under a water faucet by separatingthe liquid container from the main body. Thus, the work load isalleviated and water splashing caused during work is prevented.

In a microwave heating apparatus according to claim 24, a waste watertank is provided at a lower posi of a main body of the microwave heatingapparatus for receiving water from dew condensation in the heatingchamber and the water discharged from the boiler of the vapor generator.Since the waste water can be collected in the waste water tank,operability is improved.

What is claimed is:
 1. A microwave heating apparatus, comprising: aheating chamber for accommodating an item to be heated; a microwavegenerator for radiating microwaves to the heating chamber; and a vaporgenerator for supplying vapor to the heating chamber, wherein said vaporgenerator is configured such that the vapor is not in direct contactwith the item to be heated, and further wherein the heating chamberincludes a regenerating plate for generating and regenerating heat whenradiated by the microwaves from the microwave generator, therebyreducing dew condensation caused by the vapor in the heating chamber. 2.A microwave heating apparatus according to claim 1, wherein: the vaporgenerator includes an excitation coil provided outside a vaporgenerating chamber and a metal body provided inside the vapor generatingchamber which is made of one of foam and fiber, and water from a watersupply tank is drip-fed onto a top end of the metal body.
 3. A microwaveheating apparatus according to claim 2, wherein the vapor generatingchamber includes a diffusive member for diffusing water drip-fed fromthe water supply tank.
 4. A microwave heating apparatus according toclaim 3, wherein the diffusive member includes an end surface diffusivemember provided at an end surface of the metal body and an outerperipheral wall diffusive member provided on an outer peripheral wall ofthe metal body.
 5. A microwave heating apparatus according to claim 4,wherein the outer peripheral wall diffusive member is formed oflong-fiber assembly having an ability of absorbing liquid and an abilityof retaining liquid.
 6. A microwave heating apparatus according to claim2, wherein: the metal body includes a hollow space, and a shaft memberis inserted into the hollow space for preventing water drip-fed from thewater supply tank from flowing down from the hollow space without beingvaporized.
 7. A microwave heating apparatus according to claim 6,wherein the shaft member is a rolled cylindrical member which has asufficient spring property to vary an outer diameter thereof.
 8. Amicrowave heating apparatus according to claim 2, wherein the vaporgenerator is structured so as to pump the water up into the water supplytank by a pump through a water processing material cartridge attached tothe water supply tank.
 9. A microwave heating apparatus according toclaim 8, further comprising a control section for determining time toexchange the water processing material cartridge based on the operationtime of the vapor generator or the operation time of the pump forpumping up the water from the water supply tank, or the result ofaccumulation of amount of supplied water, and for notifying the time toexchange.
 10. A microwave heating apparatus according to claim 8,further comprising a control section for stopping the operation of thepump by detecting that the time to exchange the water processingmaterial cartridge is approaching and for allowing the operation of thepump only during a prescribed time period by detecting an inputoperation for instructing a re-start while the operation of the pump isstopped.
 11. A microwave heating apparatus according to claim 8, furthercomprising an input device for inputting a set value for the time toexchange the water processing material cartridge.
 12. A microwaveheating apparatus according to claim 2, further comprising a controlsection for notifying water supply when a water level detector detectsthat a water level in the water supply tank has reached a detectionlevel and for still continuing the operation of the vapor generator fora prescribed time period.
 13. A microwave heating apparatus according toclaim 12, wherein the water level detector includes a float having aburied magnet mounted in the water supply tank and a lead switchprovided at a position separated from the water supply tank.
 14. Amicrowave heating apparatus according to claim 12, further comprising: awater processing material cartridge, having an inlet and an outlet,attached to the water supply tank; wherein the detection level is abovesaid inlet of the water processing material cartridge.
 15. A microwaveheating apparatus according to claim 1, wherein the regenerating plateis provided on at least one of top, bottom, left, right and inner rearwalls included in the heating chamber.
 16. A microwave heating apparatusaccording to claim 1, wherein the regenerating plate is on at least oneof an upper position and a lower position with respect to a position atwhich the item to be heated is located in the heating chamber.
 17. Amicrowave heating apparatus according to claim 1, further comprising acontrol section for pre-heating the regenerating plate to a prescribedtemperature by operating the microwave generator prior to a supply ofthe vapor to the heating chamber from the vapor generator.
 18. Amicrowave heating apparatus according to claim 1, wherein a vaporspraying outlet is provided for releasing the vapor upward from a lowerposition in the heating chamber.
 19. A microwave heating apparatusaccording to claim 1, wherein a supporting plate is provided forcovering a side wall of the heating chamber and supporting ends of theregenerating plate, and the regenerating plate has a vapor directionguide formed thereon for releasing the vapor upward to a positioncorresponding to a vapor spraying outlet formed at a lower position ofthe side wall of the heating chamber.
 20. A microwave heating apparatusaccording to claim 1, wherein a length of the regenerating plate in adepth direction is shorter than a length of the heating chamber in thedepth direction, and the heating chamber is structured so that airwarmed by cooling a magnetron of a microwave generator flows in througha gap between at least one of the walls of the heating chamber and theregenerating plate which is set in the heating chamber.
 21. A microwaveheating apparatus according to claim 1, wherein a vapor spraying outletformed at the lower position on a side wall of the heating chamber isconnected to an outlet of a boiler of the vapor generator, and a lowerlevel of the vapor spraying outlet is lower than a lower level of theoutlet of the boiler.
 22. A microwave heating apparatus according toclaim 1, wherein the regenerating plate includes a plate formed of oneof ceramics or porcelain and a glaze layer formed on a surface of theplate, the glaze layer generates heat when radiated by the microwaves,and the plate regenerates the heat which is generated by the glazelayer.
 23. A microwave heating apparatus according to claim 1, furthercomprising a control section for pre-heating the heating chamber to afirst target temperature by operating the microwave generator prior tothe generation of the vapor generator when detecting a pre-heating startinstruction while being in a wait state, and also for pre-heating theheating chamber to a second target temperature which is lower than thefirst target temperature when not detecting any action during aprescribed time period.
 24. A microwave heating apparatus according toclaim 1, wherein a waste water tank is provided at a lower position of amain body of the microwave heating apparatus for receiving water fromthe dew condensation in the heating chamber and the water dischargedfrom the boiler of the vapor generator.